Hot water at home, powered by the sun, for free

As a first in southern Europe, we’re introducing a boiler that turns solar energy into hot water and cuts your power bill.

At Robinsun, we don’t just sell solar kits, we’re on a mission to give families more ways to generate the energy they need for self-consumption.

We regularly ask our customers about their needs, concerns and ideas — and many have told us that heating water is one of the biggest sources of energy consumption at home and a major part of power bills. 

Now, you can cover that too, with our brand new solar water boiler. More independence, more savings, same clean energy from the sun.

How does it work?

Water is heated by one or two electric rods inside the tank, depending on the system you choose. These rods convert energy from photovoltaic solar panels directly into heat, warming the water efficiently.

In 80 or 120 l tanks with a single lower-side entry, the controller comes with one hybrid rod that runs primarily on solar power. In specific moments, such as cloudy days or after heavy water usage, it can smartly switch to the grid to ensure you always have hot water.

In 200 or 300 l tanks with two entry points, we use a dual-rod system, with a fully solar-powered rod at the bottom and a hybrid rod at the top, guaranteeing all-time comfort and uninterrupted access to hot water.

This setup ensures the top of the tank heats just as much as the bottom, with no cold layers, just consistent, reliable warmth managed by a smart controller.

Heating water to 65 °C is not only ideal for comfort, but also crucial for health, as it is the recommended temperature to keep your water purified and free from harmful bacteria.

What makes this system different

This solution combines our performance solar panels, a smart electronic controller that acts as a microinverter, one or two powerful heating rods, and a storage tank. It converts the energy produced by the panels into heat directly and efficiently.

Unlike traditional solar thermal systems — which use large, clunky rooftop collectors that heat water directly inside and are complex to install — our system uses the same solar panels found in our plugin solar kits. These connect to the controller and generate electricity, which is then transformed into heat inside the tank by the rods.

Another key advantage is performance. Our system heats water up to three times faster than others on the market. You’ll have hot water available from the very first moment, while other systems may take up to 10 hours to reach full temperature due to weaker rods.

Made in Germany

We partnered with German manufacturer Nexol for their unmatched efficiency, reliability, and innovation in solar water heating. Their expertise ensures you get a system built to last, engineered for comfort, and optimized for real savings.

With a Nexol water heating system, your savings are always significant. Compared to electric boilers, you can reduce your energy costs by up to 75%. The system utilizes over 90% of the power generated by your panels.

Our water tanks are also made in Germany by SHWT, a leading manufacturer known for high-quality engineering. Their advanced insulation keeps the water hot for longer, reducing the need for reheating. Combined with the smart controller, the system heats water faster and keeps it warm even after sunset so you can enjoy a hot shower any time of day.

Meet the NEX-R series – Choose the right size for your home

Nexol’s NEX-R series is easy to install thanks to its plugin design and can fully meet your hot water needs on sunny days, while helping reduce heating costs significantly in winter.

Available in different sizes and formats, it adapts to any household's needs. Each model comes with a controller, water tank, and heating rods, ready to connect to your solar panels.

Since the solar panels are connected to the controller and not to the grid, you can add as many panels as you need. You don’t have to worry about maximum output, because everything is managed by the Nexol smart controller, and no surplus is sent to the grid.

The number of panels will depend on the size of your water tank and the specifics of your solar panel installation.

We recommend an ideal minimum number of panels for each model, but you can always connect more in series if needed.

NEX RS 80 l

Wall-mounted version that includes a controller, an 80 liter water tank, and one heating rod integrated into the base of the tank. Easy to install and designed to deliver maximum comfort for small homes.

To heat the 80 liters of this tank, you will need 2 of our high-performance solar panels.

NEX RS 120 l

Wall-mounted version that includes a controller, a 120 liter water tank, and one heating rod integrated into the base of the tank. Easy to install and designed to deliver maximum comfort for small to medium-sized homes.

To heat the 120 liters of this tank, you will need between 2 and 4 of our high-performance solar panels, depending on your location and the type of installation.

NEX RS 200 l

The floor-standing version comes with our controller, a  200-liter tank and one or two heating rods installed in the upper part of the tank, powered primarily by solar energy with optional grid backup. Perfect for medium-sized homes.

We recommend using at least 4 of our high-performance solar panels to heat this tank efficiently, but you can always add more if your installation or energy needs require it.

NEX RS 300 l

The ideal choice for heating large water volumes. This model features a dual-rod system combined with a smart temperature controller that prioritizes solar energy throughout the day to heat your water efficiently.

The lower rod operates entirely on solar power, while the upper hybrid rod is managed by a smart sensor that monitors the temperature and activates the grid only when necessary, ensuring hot water is always available, especially in the part of the tank used first.

This intelligent setup guarantees comfort at all times, even on cloudy days. The kit includes the controller, a 300 liter tank, and two heating rods.

We recommend using at least 4 of our high-performance solar panels for optimal performance, although the exact number may vary depending on your location and installation conditions and you can always add more if your installation or energy needs require it.

Full control from the start

The controller’s display lets you see, in real time, how much energy you're generating and how it’s being used. You can also choose when the grid should kick in, giving you full control over your consumption and savings.

A big advantage of this system is that it uses the same solar panels as our regular solar kits. This means you can generate clean energy for your home and heat your water using just one type of panel.

For example, if you install 8 panels on your roof or in your garden, you can connect 4 to a microinverter plugged into the grid for your daily electricity needs, and the other 4 to the boiler’s controller to produce hot water, covering almost all of your energy consumption, all powered by the sun.

Conclusion

This system is designed for homes that want to move away from gas, reduce their reliance on the grid, and harness free solar energy all year round. With optimized consumption, smart control, and simple installation, we’re taking another step toward a more sustainable future.

Whether you need a small, medium or large system, we’ve got the ideal solution to eliminate the biggest part of your power bill.

If you have questions, contact us via email, WhatsApp or call us directly.